Carbon monoxide sensor for an engine assembly

ABSTRACT

An engine assembly includes an internal combustion engine and a carbon monoxide (CO) sensor unit. The CO sensor unit includes a CO sensor controller including a CO sensing circuit configured to detect a level of CO and a shutdown circuit. The shutdown circuit is configured to receive a detected level of CO and calculate a trailing window average of the detected level of CO. The trailing window average includes an average of the detected level of CO over a predetermined sampling window. The shutdown circuit is further configured to determine whether to initiate a shutdown of the internal combustion engine based on at least the calculated trailing window average and a predetermined trailing window average threshold and initiate the shutdown of the internal combustion engine based on determining that the trailing window average exceeds the predetermined trailing window average threshold.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/991,327, filed May 29, 2018, which claims the benefit of U.S.Provisional Application No. 62/512,623, filed May 30, 2017, the contentsof which are each incorporated herein by reference in their entireties.

BACKGROUND

The present invention generally relates to internal combustion engines.More specifically, the present invention relates to a carbon monoxide(CO) detection system for a portable generator powered by an internalcombustion engine.

SUMMARY

One embodiment of the invention relates to an engine assembly. Theengine assembly includes an internal combustion engine and a carbonmonoxide (CO) sensor unit. The CO sensor unit includes a CO sensorcontroller including a CO sensing circuit configured to detect a levelof CO and a shutdown circuit. The shutdown circuit is configured toreceive a detected level of CO and calculate a trailing window averageof the detected level of CO. The trailing window average includes anaverage of the detected level of CO over at least two consecutivesampling loops. The shutdown circuit is further configured to determinewhether to initiate a shutdown of the internal combustion engine basedon at least the calculated trailing window average and a predeterminedtrailing window average threshold and initiate the shutdown of theinternal combustion engine based on determining that the trailing windowaverage exceeds the predetermined trailing window average threshold.

Another embodiment of the invention relates to an engine assembly. Theengine assembly includes an internal combustion engine and a CO sensorunit. The CO sensor unit includes a CO sensor controller including a COsensing circuit configured to detect a level of CO and a shutdowncircuit. The shutdown circuit is configured to receive a detected levelof CO and calculate a trailing window average of the detected level ofCO. The shutdown circuit is also configured to receive an indication ofinternal combustion engine runtime. The trailing window average includesan average of the detected level of CO over a at least two consecutivesampling loops. The shutdown circuit is further configured to determinewhether to initiate a shutdown of the internal combustion engine basedon at least (i) the calculated trailing window average and apredetermined trailing window average threshold and (ii) based on thecomparison of the internal combustion engine runtime and a predeterminedruntime period. The shutdown circuit is configured to initiate theshutdown of the internal combustion engine based on determining that thetrailing window average exceeds the predetermined trailing windowaverage threshold. The predetermined trailing window average thresholdis adjusted upon determine the internal combustion engine runtimeexceeds the predetermined runtime period.

Another embodiment of the invention relates to a method of controllingan internal combustion engine. The method includes a step of sensing alevel of CO with a CO sensor. The method further includes a step ofcalculating a trailing window average of the sensed level of CO over atleast two consecutive sampling loops with a CO sensor controller. The COsensor controller then compares the calculated trailing window averageof the sensed level of CO to a predetermined trailing window averagethreshold. The CO sensor controller can then send a command to terminateoperation of the internal combustion engine to the internal combustionengine upon determining that the trailing window average of the sensedlevel of CO exceeds the predetermined trailing window average threshold.

Alternative exemplary embodiments relate to other features andcombinations of features as may be generally recited in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure will become more fully understood from the followingdetailed description, taken in conjunction with the accompanyingfigures, in which:

FIG. 1 is a perspective view of a generator according to an exemplaryembodiment;

FIG. 2 is a schematic diagram of the generator of FIG. 1;

FIG. 3 is a schematic diagram of a carbon monoxide detection sensor ofthe generator of FIG. 1;

FIG. 4 is a flow chart of a method of determining a transient value andcalculating a sum of transient values, according to an exemplaryembodiment;

FIG. 5 is a flow chart of a method of monitoring CO levels and shuttingdown the generator, according to an exemplary embodiment;

FIG. 6 is a flow chart of a method of transitioning the generator COsensing mode from a start-up mode to a continuous mode, according to anexemplary embodiment;

FIG. 7 is a graph of generator operating time versus carbon monoxidedetection levels for an outside condition and an inside condition;

FIG. 8 is a graph of generator operating time versus carbon monoxidedetection levels;

FIG. 9 is a graph of generator operating time versus carbon monoxidedetection levels;

FIG. 10 is a graph of generator operating time versus carbon monoxidedetection levels;

FIG. 11 is a schematic perspective view of the generator of FIG. 1; and

FIG. 12 is a schematic top view of the generator of FIG. 1.

FIG. 13 is a perspective view with an enlarged detail of a portion ofthe generator of FIG. 1.

DETAILED DESCRIPTION

Before turning to the figures, which illustrate the exemplaryembodiments in detail, it should be understood that the presentapplication is not limited to the details or methodology set forth inthe description or illustrated in the figures. It should also beunderstood that the terminology is for the purpose of description onlyand should not be regarded as limiting.

Referring to FIGS. 1-2, a generator is shown according to an exemplaryembodiment. The generator 10 includes an engine 12, including acarburetor 14 or other air-fuel mixing device (e.g., electronic fuelinjection, direct fuel injection, etc.), governor 16, throttle 20, airintake 22, exhaust outlet 26, and an alternator 13 driven by the engine12. The alternator 13 produces electrical power from input mechanicalpower from the engine 12. The generator 10 additionally includes one ormore outlets 15 for supply of the generated electrical power to anelectrical device of a user's choosing. The generator 10 can alsoinclude one or more wheels 17 for portability. In some embodiments, afuel tank 21 is positioned at the top of the generator 10 with theexhaust outlet 26 positioned below the fuel tank 21.

Air flows into the engine 12 from the air intake 22 and through thecarburetor 14. As air passes through the carburetor 14, the air mixeswith fuel entering the carburetor 14 from the fuel tank 21 and createsan air/fuel mixture that then enters the engine 12. The throttle 20controls the flow of the air/fuel mixture that exits the carburetor 14.The governor 16 controls the position of the throttle 20 based on adetected load on the engine 12. The air/fuel mixture leaving thecarburetor 14 is combusted in one or more cylinders of the engine 12 andexhaust gas from combustion leaves the engine 12 through the exhaustoutlet 26. The exhaust gas is primarily made up of nitrogen, watervapor, and carbon dioxide, but a portion of the exhaust gas may becarbon monoxide (CO) from incomplete combustion. Operation of agenerator (or any other equipment powered by an engine) in anon-ventilated or insufficiently ventilated enclosed or partiallyenclosed space (e.g., volume), such as a garage, home, storage unit,pop-up tent, etc., can result in accumulation of CO within the spaceover time.

As shown in FIG. 2, the generator 10 includes a CO sensor 30 configuredto detect the level or concentration of CO (e.g., parts per million(ppm)). Additionally, the CO sensor 30 may be used with other types ofoutdoor power equipment. Outdoor power equipment includes lawn mowers,riding tractors, snow throwers, pressure washers, portable generators,tillers, log splitters, zero-turn radius mowers, walk-behind mowers,riding mowers, industrial vehicles such as forklifts, utility vehicles,etc. Outdoor power equipment may, for example, use an internalcombustion engine to drive an implement, such as a rotary blade of alawn mower, a pump of a pressure washer, the auger a snow thrower, thealternator of a generator, and/or a drivetrain of the outdoor powerequipment. Portable jobsite equipment includes portable light towers,mobile industrial heaters, and portable light stands.

Referring now to FIG. 3, a schematic diagram of the CO sensor 30 isillustrated, according to an exemplary embodiment. In some embodiments,the CO sensor 30 includes a metal oxide gas sensor unit 25. The metaloxide gas sensor unit 25 detects CO concentration via a gas sensitivefilm that is composed of tin or tungsten oxides. The sensitive filmreacts with CO to determine CO concentration at the sensor unit 25. Inother embodiments, the CO sensor 30 can include an electrochemicalsensor. The electrochemical sensor measures the concentration of CO atthe sensor by oxidizing or reducing the gases at an electrode andmeasuring the resulting current.

The CO sensor 30 alerts a user to an elevated concentration of COexceeding the predetermined threshold and controls the shutdown of thegenerator 10 in these instances. Additionally, as discussed furtherherein, the CO sensor 30 includes control circuitry to determine whendetections of an elevated CO concentration may be fleeting (e.g., shortspikes in signal readings). Fleeting elevated CO concentrationdetections may be due to movement of the surrounding air rather thanunwanted accumulation of CO over a period of time. Movement of thesurrounding air can, under certain conditions, introduce the CO sensor30 to CO laden exhaust from the generator 10. This can cause transientspikes in the CO level as read by the sensor 30. For example, referringto the graph in FIG. 7, an example comparison between sensed CO levelsin an inside (e.g., enclosed) area (shown by inside generator curve 702)and in an outside (e.g., open-air) area (shown by outside generatorcurve 704) are shown. As shown, the CO levels for the inside generatorrise steadily over time and the CO levels for the outside generatorfluctuate between high and low sensed CO levels. Further, the insidegenerator curve 702 indicates a shutdown at point 706. For example, asdescribed further herein, the generator 10 may have shut down at point706 due to the transient summed array reaching the value of 40 and theTWA value exceeding 200 ppm of CO.

The CO sensor 30 includes or is coupled to a CO sensor controller 50configured to control the operations of the CO sensor 30, including butnot limited to, timing of generator shutdown and alerts, transmitting analert to a user, triggering a visual alarm (e.g., indicator light),triggering an audible alarm (e.g., alarm bell), shutting down thegenerator, etc. To perform the functions described herein, the CO sensorcontroller 50 includes a processing circuit, which includes a processorand a memory. The processor may be implemented as a general-purposeprocessor, an application specific integrated circuit (ASIC), one ormore field programmable gate arrays (FPGAs), a digital signal processor(DSP), a group of processing components that may be distributed overvarious geographic locations or housed in a single location, or othersuitable electronic processing components. The one or more memorydevices (e.g., RAM, NVRAM, ROM, Flash Memory, hard disk storage) maystore data and/or computer code for facilitating the various processesdescribed herein. Moreover, the one or more memory devices may be orinclude tangible, non-transient volatile memory or non-volatile memory.Accordingly, the one or more memory devices may include databasecomponents, object code components, script components, or any other typeof information structure for supporting the various activities andinformation structures described herein.

In some embodiments, the CO sensor 30 and CO sensor controller 50 form aCO sensing system. The CO sensor 30 and CO sensor controller 50 can bepackaged as a unit within a shared housing or packaged separately fordetection of CO. In some embodiments, the CO sensor controller 50 isincorporated into a controller tasked with other controlresponsibilities in an end product (e.g. incorporated into the enginecontroller or other controller of an automobile). In this way, the COsensor 30 and/or CO sensor controller 50 can be used to detect CO andshut down an engine used with any type of equipment. For example, the COsensor 30 and/or CO sensor controller 50 can be used on a vehicle todetect CO levels and/or accumulation resulting from vehicle exhaust andshut down an engine on the vehicle in response to a determination ofaccumulation or high levels of CO.

The CO sensor controller 50 includes a CO sensing circuit 52, a shutdowncircuit 54, and an alert circuit 56, with all such circuits communicablycoupled to each other. The CO sensing circuit 52 is configured toreceive sensor output values from the CO sensor 30 relating to thedetected CO concentration and communicate the CO concentration to theshutdown circuit 54 and alert circuit 56. Accordingly, the CO sensingcircuit 52 is communicably and operatively coupled to the shutdowncircuit 54 and alert circuit 56 to provide the CO concentration values.In some embodiments, the CO concentration values may be provided interms of output voltage values which are proportional to the CO ppmvalues. The CO sensor controller 50 may additionally include a databaseconfigured to store sensed CO values over time and correspondingresponse actions (e.g., generator shutdown, alert transmission, alertsignal, self-diagnostics, etc.). The CO sensor controller 50 may alsoinclude a temperature sensor configured to sense the ambient temperaturesurrounding the generator 10. The sensed temperature values can be usedto adjust the CO sensed values to accommodate for sensed temperature.The sensed temperature may be an indication of a generator runningenvironment as the sensed temperature surrounding a generator inside maybe higher than that of a generator running outside.

The shutdown circuit 54 is configured to receive the detected CO valuesfrom the CO sensing circuit 52, determine whether the generator 10 islikely in an enclosed space, an open space, a small enclosed space, alarge enclosed space, a semi-enclosed space, or outdoor space anddetermine whether to shut down the generator 10 and/or provide atriggered alarm response to the detection. Upon receiving the detectedCO concentration values (e.g., correlating output voltage values) fromthe CO sensor 30, the shutdown circuit 54 first determines if thegenerator 10 is likely in an enclosed space or an open space. Dependingon indications of whether the generator 10 is in an open or enclosedspace, the shutdown circuit 54 will treat sensed CO concentration datadifferently. To determine the environment of the generator 10, theshutdown circuit 54 may use a variety of methods. In many of themethods, the shutdown circuit 54 uses time lapse information to performcalculations. Accordingly, a timing circuit may be included with thegenerator 10 to determine the amount of time the generator 10 has beenrunning. To determine run time, electrical output from the generator,spark plug data, and/or electric starter data may be used to determinethe start of the generator operation, the duration of generatoroperation, the number of engine starting or stopping events within acertain period of time, etc. Additionally, calculations may be reset dueto a sensed movement of the generator 10. Movement of the generator 10can be sensed via a piezoelectric sensor positioned on the generator 10configured to measure acceleration data.

The shutdown circuit 54 may additionally set an absolute maximum COconcentration threshold such that upon reaching the threshold, thegenerator 10 is shut down. Accordingly, at any point in time regardlessof the environment in which the generator 10 is positioned, when anabsolute CO threshold concentration (e.g., >300 ppm of CO) is detected,the generator 10 is shut down.

In some embodiments, the shutdown circuit 54 also uses the overalllapsed time since the generator 10 was started to determine a sensedvalue threshold for shut down. For example, for a time period of lessthan twelve minutes, the shutdown circuit 54 uses one set of thresholdvalues to determine when to shut down the generator 10 and for one ormore subsequent operating periods (e.g., greater than twelve minutes,etc.), the shutdown circuit 54 uses a different set of threshold values.For the initial operating period, the shutdown circuit 54 has lowerthreshold values for triggering a shutdown or alarm than the subsequentoperating periods. Any false alarm or shutdown triggers may be lessinconvenient to a user while the user is still near the generator 10(e.g., less time has passed), than if the user has already left thearea. In other embodiments, other time periods can be used. Once thegenerator 10 moves into subsequent operating periods, the controller canbe more confident that the generator is not operating in an enclosedspace and can reduce the sensitivity and reduce the occurrence ofunwanted shutdowns. Because CO typically accumulates quickly in anenclosed space, it is beneficial to be relatively sensitive to elevatedCO concentrations in that environment to shut down the generator.

In addition to monitoring the current CO concentration value, theshutdown circuit 54 calculates and monitors a trailing window average(TWA) of the sensed CO concentration values. To continually monitor theTWA, the shutdown circuit 54 uses current and past sensed COconcentration values for a single generator run. In this regard, theshutdown circuit 54 may temporarily store the readings relating to oneor more data samples in a database incorporated with the CO sensorcontroller 50. To calculate the TWA, the shutdown circuit 54 uses theequation below for each sample reading time frame.

${TWA} = {{TW{A_{old}\left( \frac{n_{TWA} - 1}{n_{TWA}} \right)}} + {{ppm}_{{current}\mspace{14mu}{reading}}\left( \frac{1}{n_{TWA}} \right)}}$

In the above equation, “TWA_(old)” is the prior loop value of the TWA,“n_(TWA)” is the number of loops over which the value is averaged, and“ppm_(current_reading)” is the sensed CO concentration value.

By determining the TWA of the sensed CO concentration values using anequation such as the one above, as well as other factors describedherein, the shutdown circuit 54 determines whether the generator 10 isin an enclosed space (e.g., garage) and potentially experiencing settledaccumulations of CO or in an open space (e.g., outside) and experiencingbrief spikes in readings of the CO concentrations (e.g., due to airmovement surrounding the generator 10). The TWA of the sensed valuesindicates the amount of data points that are either rising or fallingwith respect to past sensed values, and thus, can be used as a factor indetermining if accumulation is occurring over time.

The current loop calculated TWA value is compared against the prior loopTWA value to set a binary transient value. A binary transient value isset to either a value of one or a value of zero based on therelationship between the prior loop TWA values and the current loopcalculated TWA values. If the current TWA loop value is greater than theTWA value by at least a threshold value (e.g., 1 ppm), the binarytransient value is set to one. If the current TWA loop value is lessthan a threshold value above the prior loop TWA value, the binarytransient value is set to zero (see FIG. 9). As an example, thethreshold value can include 1 ppm of CO. In another example, thethreshold value is more or less than 1 ppm of CO. In other examples, thethreshold value may be expressed as a percentage (e.g., +/−5% of the TWAvalue). The binary transient values are stored in a pre-sized array andall stored binary transient values in the array are summed to calculatea summed array value. The summed array value is used in connection withother factors to determine whether to shut down the generator 10, asdescribed further herein. The members of the array and therefore the sumof the array are reset to zero upon detection of a current TWA valueless than the threshold above the prior TWA. The size of the arraycorresponds to the number of data points desired to be summed tocalculate a summed array value. For example, the pre-sized array mayinclude 40 data points, such that the summed array value includes thesum of all 40 data points.

As described further herein, various conditions may trigger a generatorshutdown and/or alert. In one condition representing a small or mid-sizeenclosure with rapid CO level rise, if the generator is still in aninitial operating mode (e.g., start-up mode, less than a predeterminedtime period), the TWA equals or exceeds a first TWA threshold, and thesummed array value equals a predetermined sum threshold, a generatorshutdown and/or alert is triggered. As an example, in this condition,the initial operation may last for approximately twelve minutes, thefirst TWA threshold may be 200 ppm of CO, and the predetermined sumthreshold equals 40 (equaling the number of data points in the binarytransient array). Accordingly, in this example, if the generator hasbeen running for less than twelve minutes, the TWA value equals orexceeds 200 ppm of CO, and the summed value equals 40, a shutdown and/oralert is triggered. If one or more of these conditions is not met, theshutdown and/or alert is not triggered.

In a second condition, if the generator is past an initial operatingcondition (e.g., more than a predetermined time period of twelveminutes) and the TWA equals or exceeds a second TWA threshold (e.g.,equal to or exceeding 300 ppm), a shutdown and/or alert is triggered. Asan example, for a shutdown and/or alert to be triggered in thiscondition, the generator has been running for more than twelve minutesand the TWA exceeds a 300 ppm of CO threshold. Regardless of whether ina start-up mode (e.g., less than twelve minutes) or in a continuous mode(e.g., more than twelve minutes), a TWA value exceeding 300 ppm invokesa shutdown. In some embodiments, the number of loops used to calculatethe TWA value in a start-up mode is 5 loops and the number of loops usedto calculate the TWA value in a continuous mode is 70 loops.

Another condition of shutdown, which is configured to protect againstsemi-enclosed generator running (e.g., under a pop-up canopy or in agarage with an open garage door), includes monitoring the TWA in longerwindows of time and if during the monitoring window the TWA remainsabove a certain threshold of CO, a shutdown procedure will be triggered.For example, if the TWA exceeds a limit of 200 ppm for more than 120loops (not necessarily contiguous), a shutdown is invoked. The count ofthe loops with a TWA value of greater than 200 ppm may be referred to asthe “alcove count.” The alcove count is reset to zero if the current TWAvalue is more than 75 ppm below the maximum TWA value recorded since thestart of the generator 10. The alcove count protection runs in both astart-up mode and a continuous mode.

The combination of parameters including generator runtime, TWA, summedarray value, and currently sensed CO level (ppm) can be combined to bestguard against CO accumulations during enclosed space running, whileminimizing nuisance shutdowns. During initial operation (e.g., less thantwelve minutes), the TWA of sensed CO levels is monitored to a higherthreshold. As an example, a generator shutdown is triggered if a TWA ofCO concentrations is greater than or equal to a threshold of 200 ppm ofCO and the summed array value is equal to the array size (e.g., summedarray value equals 40) or if the TWA is greater than or equal to athreshold of 300 ppm of CO. Conversely, if run-time is greater thantwelve minutes, a generator shutdown is not triggered for detected COconcentrations until a TWA of sensed CO levels is higher than 300 ppm.

To provide further protection against nuisance shutdowns during theinitial operation of the generator (e.g., during a start-up mode, lessthan twelve minutes), if the TWA of the sensed CO levels is monitored todrop by more than a predetermined threshold (e.g., 75 ppm) below themaximum TWA value since the startup of the generator 10, the monitoringmode of the generator is changed from a start-up mode to a continuousmode, as described further herein with regard to FIG. 6. The start-upmode is the monitoring mode during the initial operation of thegenerator 10 and the continuous monitoring mode is the monitoring modeafter the initial operation of the generator 10. If the TWA of thesensed CO levels drops by more than the threshold, this is an indicationof the generator 10 being located in an open-air area, where airmovement may cause great fluctuations in the sensed CO levels. Bychanging the monitoring mode from a start-up mode to a continuous mode(e.g., from a more stringent to a less stringent monitoring mode), lessnuisance shutdowns may occur.

In some embodiments, the shutdown circuit 54 may additionally oralternatively use other calculation methods to determine whether thegenerator 10 is in an enclosed or an open space. The shutdown circuit 54may use any method to detect and amplify the characteristics (e.g.,choppy versus smooth) of the detected CO concentration versus timecurve. For example, variance, standard deviation, variance of the firstderivative, peak-to-peak range, curve kurtosis, or other customfunctions may be used to determine the environment of the generator 10.

The shutdown circuit 54 can use various other sensors to determinewhether the generator 10 is in an enclosed or an open space. The sensorscan include, but are not limited to, an ambient lighting sensor, anacoustic sensor, radar sensor, wind speed sensor, Global PositioningSystem (GPS) mapping, and so on.

Once the shutdown circuit 54 has determined whether the generator 10 isin an enclosed or open space, the shutdown circuit 54 triggers shutdownand/or alerts upon detection of a predetermined threshold for thatenvironment. In this regard, the shutdown circuit 54 is coupled to anengine shutdown circuit of the engine 12 to complete a shutdownprocedure. The shutdown procedure may include grounding the generatorignition for a period of time (e.g., 10 seconds) until the engine 12 isturned off. The shutdown circuit 54 is also communicably and operativelycoupled to the alert circuit 56 to communicate an indication that athreshold level has been reached for an alert to be triggered. The alertmay be paired with a shutdown of the generator 10 and/or a warning ofpotentially elevated CO concentration without shutting down thegenerator 10. Accordingly, the alert may include illuminatinglight-emitting diodes (LEDs) on the user interface of the generator 10to indicate that the generator is being or has been shut down.

After the generator has been shut down, the shutdown circuit 54 isfurther configured to remain in an active mode, where the shutdowncircuit 54 is actively monitoring and preventing restart of thegenerator 10, for a period of time (e.g., 15 minutes). Accordingly, if auser tries to restart the generator 10 during this time, the shutdowncircuit 54 will prevent the starting of the generator 10 and effectively“lock-out” the user from using the generator 10 during that time. Assuch, a user is prevented from restarting the generator 10 and furtheraccumulating CO during times when the generator has been shut down basedon high sensed CO concentrations. In some embodiments, instead oflocking out the user, the generator 10 may be allowed to restartbriefly, but immediately shutdown if a CO level threshold trigger isdetected again. This may be advantageous to power management (e.g.,battery life) of the system.

The alert circuit 56 is configured to communicate with the shutdowncircuit 154 to receive an indication that the generator 10 has been shutdown due to sensed CO accumulation or an indication of an elevated COconcentration. The alert circuit 56 is additionally configured totrigger a CO notification 70 (e.g., alarm system) on the generatorincluding, but not limited to, an indicator light and an audible alarm.In this configuration, if the user is signaled that the shutdown is dueto CO emissions build-up in a non-ventilated space, the user is lesslikely to try to start the generator back up. The alert circuit 56 maytrigger varying levels of alarms corresponding to the sensedconcentration of CO, with alarm severity increasing with the increasingCO concentration (e.g., warning light, warning audible alarm and thenshut down, etc.). In some embodiments, the alert system is powered by aseparate power supply than the sensing element (e.g., sensor unit 25) toprolong the shutdown capability of the system, described further herein.

In some embodiments, the alert circuit 56 is configured to switch over amechanical switch to an elevated CO concentration indication positionwhen a shutdown of the generator 10 occurs due to the detection ofaccumulated CO. Accordingly, the user will be notified of the COdetection by the physical location of the switch even though thegenerator 10 has been shut down and no electrical (e.g., sound or light)indication may be present. In the case of a shutdown switch, beforestarting the generator 10 back up after a shutdown, the user must firstphysically move the switch from the elevated CO concentration indicationposition back to an operating position. In some embodiments, thegenerator 10 may additionally include tamper resistant sensors.Accordingly, a user cannot easily disconnect or circumvent the sensorsdescribed herein. For example, power and communication wires to and fromthe CO sensor 30 may be combined in a single wire harness.

In some embodiments, the alert circuit 56 is additionally configured tocommunicate with a mobile device to alert a user that the generator 10has been shut down due to sensed CO accumulation. Accordingly, the usermay be alerted on the mobile device while the user is away from thegenerator 10 and can proceed with caution if re-entering the enclosedspace.

One or more batteries are included to power the components of the COsensor 30 and CO sensor controller 50. In some embodiments, thebatteries are lithium-ion coin cell batteries. In other embodiments, thebatteries may use different battery chemistries and/or structuralconfigurations. A sensor battery 60 is coupled to the CO sensor unit 25,the CO sensing circuit 52, and the shutdown circuit 54 to provide powerto the sensing, detection, and shutdown operations of the generator 10.The sensor battery 60 continues to provide power to the CO sensor unit25 even when the generator 10 is shut down. This way, the CO sensor unit25 is still actively monitoring CO concentration (e.g., via pulsedetection) when the generator 10 is not running. The continuousoperation of the CO sensor unit 25 allows the unit 25 to continue tomonitor the CO concentration in the vicinity of the generator 10 (e.g.,every three minutes) and prevents the unit 25 from resetting thebaseline CO reading to zero ppm upon turning off power from thegenerator to the sensor unit 25. Without continuous supply of power tothe sensor unit 25 from the sensor battery 60, the sensor unit 25 maynormalize the CO reading to zero ppm upon receiving power (even in areaswith CO present), and accordingly, the CO reading may be skewed if poweris not continuously supplied to the CO sensor unit 25.

An auxiliary battery 62 can also be coupled to the CO sensor 30 toprovide power to the auxiliary systems included with the CO sensor 30,such as the alert circuit 56 and the CO notification 70 (e.g., alertlight, audible alarm, sensor self-diagnostics, etc.). Like the sensorbattery 60, the auxiliary battery 62 may also provide continuous powerto the auxiliary systems of the sensor 30. Accordingly, an alert maystill be transmitted, sounded, lit, etc. and self-diagnostics are stillperformed when the generator 10 is off.

The CO sensor 30 is continuously running self-diagnostics. If a problemis detected, such as low sensor battery, low alert battery, missingsensor module, the sensor is shorted, the sensor electrolyte is driedout, the sensor has reached the end of its sensor life, etc., an alertnotification is triggered (e.g., red LED is illuminated once every 10seconds) and the ignition is grounded to shut down the generator 10. Thesensor failure mode triggers a lock-out condition such that a usercannot restart the engine 12 until the CO sensor 30 (e.g., sensor unit)is replaced. In some embodiments, instead of locking out the user, thegenerator 10 may be allowed to restart briefly, but immediately shutdownif a CO level threshold trigger is detected again.

Referring to FIG. 4, a method for setting and summing binary transientvalues is shown, according to an exemplary embodiment. The method 100includes sensing a CO concentration level at 102. The CO concentrationlevel is sensed by the CO sensor 30. The CO concentration level isreceived by the shutdown circuit 54 for monitoring, as described furtherherein.

A generator runtime value is determined at 104. The generator runtimevalue may be tracked by a timing circuit incorporated with the CO sensorcontroller 50. Accordingly, a timing circuit may be included with thegenerator 10 to determine the amount of time the generator 10 has beenrunning. As noted above, to determine run time, electrical output fromthe generator, spark plug data, and/or electric starter data may be usedto determine the start of the generator operation, the duration ofgenerator operation, the number of engine starting or stopping eventswithin a certain period of time, etc.

A TWA of sensed CO concentration values is calculated at 106. As shownabove in the equation for calculating TWA, the TWA is determined usingthe current CO concentration level, a prior loop value of TWA, and thenumber of loops over which the value is averaged. Next, it is determinedwhether the sensed CO concentration value is greater than a thresholdabove the calculated TWA at 108. If the sensed CO concentration value isless than the threshold above the TWA, the transient value is set tozero and all array values are set to zero (e.g., effectively resettingthe summed array value to zero) at 110. If the sensed CO concentrationvalue is greater than a threshold above the TWA, the transient value isset to one at 112. The current transient value is then summed with thepreviously calculated transient values to determine a summed array valueat 114.

Referring to FIG. 5, a method for determining whether to shut down thegenerator is shown, according to an exemplary embodiment. The method 100includes determining a generator runtime value at 202. The generatorruntime value may be determined similarly to step 104 in method 100(FIG. 4). The TWA is calculated at 204. The TWA may be calculated inaccordance with the equation above and step 106 of method 100 (FIG. 4).The summed array value is calculated at 206. The summed array value maybe calculated similarly to steps 108-114 in method 100 (FIG. 4).

Next, it is determined whether the generator runtime value exceeds apredetermined runtime value at 208. In one embodiment, the predeterminedruntime value is twelve minutes. In other embodiments, the predeterminedruntime value can be more or less than twelve minutes (e.g., between 10and 20 minutes).

If the generator runtime value does not exceed the predetermined runtimevalue at 208, it is determined whether the TWA equals or exceeds a firstTWA threshold at 210. As an example, the first TWA threshold may be setto 200 ppm of CO. The first TWA threshold may correlate to a lower TWACO concentration limit. This lower limit of CO concentration may be usedduring a start-up monitoring mode. The start-up monitoring mode is usedduring runtime of the generator under the predetermined runtime value(e.g., less than six minutes) and in combination with the summed arrayvalue described below to determine whether to shut down the generator orprovide a notification of high levels of CO concentration.

If the TWA equals or exceeds a first TWA threshold at 210, it isdetermined whether the summed value is equal to a predetermined sumthreshold at 212. In an exemplary embodiment, the summed value beingequal to the sum threshold indicates that all numbers in the transientarray are equal to one. As an example, with the 48 data point arraydescribed above, the sum threshold would equal 40 such that if all datapoints in the array are equal to one, the sum array is equal to 40 andthus, equal to the sum threshold. In other embodiments, thedetermination may include whether the summed value is exceeds apredetermined sum threshold, where the sum threshold is less than thesize of the array.

If the TWA equals or exceeds the first TWA threshold at 210 and thesummed value is equal to the predetermined sum threshold at 212, a COnotification is triggered and/or the generator is shut down at 214. Insome embodiments, step 214 includes communicating an indication of thepresence of CO concentration to the alert circuit 56. The alert circuit56 and various shutdown and notification arrangements are describedfurther herein.

If the generator runtime value does not exceed the predetermined runtimevalue at 208, it is determined whether the TWA equals or exceeds asecond TWA threshold at 216. The second TWA threshold may correlate to ahigher TWA CO concentration limit. This higher limit of CO concentrationmay be used during a continuous monitoring mode. The continuousmonitoring mode is used during runtime of the generator exceeding thepredetermined runtime value (e.g., over six minutes). If the TWA equalsor exceeds the second TWA threshold, a CO notification is triggeredand/or the generator is shut down at 214.

If the variance is calculated to be relatively high, the shutdowncircuit 54 determines that the generator 10 is positioned in an openenvironment and may use a different sensed CO threshold to shut down thegenerator 10 than if the variance is calculated to be relatively low. Asan example, if the variance is calculated to be relatively low, theshutdown circuit 54 determines that the generator 10 is likelypositioned in an enclosed space and shuts down the generator 10 at alower CO ppm reading or within a smaller time frame than if determinedto be in an open space.

Referring to FIG. 6, a method of switching from a start-up mode to acontinuous mode for CO concentration level monitoring is illustrated,according to an exemplary embodiment. The method 300 includesdetermining a generator runtime value at 302 and calculating a TWA at304, which may be completed in accordance with steps 104 and 106 ofmethod 100, respectively.

Next, it is determined whether the generator is in a start-up mode at306. The generator is in a start-up mode during the first predeterminedtime period of running (e.g., the predetermined generator runtime valuein method 200). Accordingly, a start-up mode can be determined bycomparing the first predetermined time period against the generatorruntime value. If the generator runtime value is less than the firstpredetermined time period, the generator is in a start-up mode. If thegenerator runtime value is greater than the first predetermined timeperiod, the generator is not in a start-up mode (e.g., is in acontinuous monitoring mode).

A subsequent TWA is calculated at 308. The subsequent TWA is calculatedin the same manner as the TWA value at step 304 and additionallyincludes the calculated TWA value of step 304 as the previous loop TWAvalue (TWA_(old)) in the TWA calculation above.

It is determined whether the subsequent TWA is less than the TWA bygreater than a predetermined drop threshold at 310. As an example, thepredetermined drop threshold may be 75 ppm. The predetermined dropthreshold may be more or less than 75 ppm. If the subsequent TWA is lessthan the TWA by greater than the predetermined drop threshold, thegenerator is switched into a continuous monitoring mode. Accordingly, inthe example, if the subsequent TWA value is less than the TWA by morethan 75 ppm, the generator is switched into a continuous monitoring modeat 312.

The continuous monitoring mode is the CO level monitoring mode when thegenerator has been running for longer than the first predetermined timeperiod (e.g., six minutes), as discussed above with regard to step 306.After the first predetermined time period, the monitoring mode for thegenerator switches from a start-up mode to a continuous mode. Using themethod 300 described above, the time the generator is in the start-upmode may be shortened due to an indication of a sudden high drop-off inCO levels. A sudden high drop-off in CO levels may be an indication thatthe generator is positioned in an outside, non-enclosed area. Theswitchover from the start-up mode to a continuous mode due to a highdrop-off in CO levels regardless of generator runtime may protectagainst nuisance shutdowns of the generator. Allowing for switchoverfrom the start-up mode to a continuous mode due to high drop-offs in COlevels also allows for a longer start-up mode run time (e.g., sixminutes) where a generator running in a particularly large space (e.g.,parking garage, construction site) that may be slow to accumulateconcentrations of CO can be monitored.

Referring to FIG. 8, a graph of generator run time versus sensed COlevels is illustrated. Graph 800 illustrates a current CO level curve802 graphed against a calculated TWA curve 804. The CO level curve 802increases more rapidly as the TWA curve 804 steadily increases. Asshown, the CO level curve 802 starts above the TWA curve 804, dips belowthe curve 804 at point 805, surpasses the TWA curve 804 again at point806, and remains above the TWA curve 804 for the remainder of the graph800. This type of behavior may be indicative of an enclosed runninggenerator due to the steady rise of CO levels. The CO level curve 802reaches above a threshold above the TWA curve 804 shown as 808. At thispoint, as described above, the binary transient values are set to avalue of one. Prior to this, the binary transient values were set to avalue of zero. Accordingly, the steady rise of the CO level curve 802will result in the summed array value increasing over time.

Referring to FIG. 9, a graph of generator run time versus sensed COlevels is illustrated. Graph 900 illustrates a current CO level curve902 graphed against a calculated TWA curve 904. As shown, at point 906,the current CO level curve 902 is above a threshold above the TWA curve904 such that the binary transient value will be set to one. At point908, the current CO level curve 902 is below the TWA curve 904 such thatthe binary transient value will be set to zero. During window 910, theCO level curve 902 fluctuates rapidly such that it extends below andabove the TWA curve 904.

Referring to FIG. 10, a graph of generator run time versus sensed COlevels is illustrated. Graph 1000 illustrates a calculated TWA curve1002. As shown, the TWA curve 1002 drops by a drop value 1004 within ashort period of time. This CO drop-off behavior indicates that thegenerator may be in an open-air area where high fluctuations of COlevels may be read by the sensor 30. Accordingly, the drop-off behaviorprompts the shutdown circuit 54 to switch the monitoring mode from astart-up mode to a continuous mode (e.g., method 600 in FIG. 6) at thepoint of the drop value 1004.

Referring to FIGS. 11-12, the generator 10 includes a front 32, rear 34,top 36, bottom 38, left side 40, and right side 42. As shown in FIG. 11,the CO sensor 30 is positioned on the right side 42 near the front 32,while the exhaust outlet 26 is positioned on the left side 40 near therear 34. In other embodiments, the CO sensor 30 may be positioned onanother side of the generator 10 (e.g., front 32). While not limited tothe exact positioning illustrated in FIGS. 11-12, the positioning of theCO sensor 30 is preferably selected such that exhaust gases exiting theexhaust outlet 26 are not blown back directly onto the CO sensor 30 inan environment with wind and/or air movement toward the exhaust outlet26. Accordingly, when viewing the generator 10 from above as shown inFIG. 12, the CO sensor 30 is positioned on an opposite side of thegenerator 10 from the exhaust outlet 26 (e.g., diagonally opposite,directly opposite). In some embodiments, when viewed from above, the COsensor 30 is positioned on an opposite side of the generator 10 from theengine 12 with the engine 12 located between the sensor 30 and theexhaust outlet 26. Positioning the sensor 30 as described helps tobroaden the difference in variance seen in enclosed space versus openspace running.

Additionally, the CO sensor 30 is positioned at an elevation lower thanthe exhaust outlet 26. Due to the relatively higher temperature ofexhaust gases compared to atmospheric temperatures, the exhaust gaseswill rise upon exit from the exhaust outlet 26. Accordingly, positioningthe CO sensor 30 at an elevation lower than the exhaust outlet 26 helpsto prevent the continuous passing of exhaust gases over the CO sensor 30during normal operation, while still allowing detection of elevatedconcentrations of CO due to accumulation over a period of time.

Referring to FIG. 13, another arrangement of the generator 10 and COsensor 30 is shown, according to an exemplary embodiment. As shown, theCO sensor 30 includes the CO sensor controller 50, and CO notification70 (e.g., alert light) as part of one CO sensor unit. The generator 10includes the CO sensor 30 positioned (e.g., mounted using mountingfeature 75) on the front 32 near the top 36 of the generator 10, whilethe exhaust outlet 26 is positioned on the rear 34 near the bottom 38.As described above, the positioning of the CO sensor 30 is preferablyselected such that exhaust gases exiting the exhaust outlet 26 are notblown back directly onto the CO sensor 30 in an environment with windand/or air movement toward the exhaust outlet 26.

The embodiments described herein have been described with reference todrawings. The drawings illustrate certain details of specificembodiments that implement the systems, methods and programs describedherein. However, describing the embodiments with drawings should not beconstrued as imposing on the disclosure any limitations that may bepresent in the drawings.

It should be understood that no claim element herein is to be construedunder the provisions of 35 U.S.C. § 112(f), unless the element isexpressly recited using the phrase “means for.”

As used herein, the term “circuit” may include hardware structured toexecute the functions described herein. In some embodiments, eachrespective “circuit” may include machine-readable media for configuringthe hardware to execute the functions described herein. The circuit maybe embodied as one or more circuitry components including, but notlimited to, processing circuitry, network interfaces, peripheraldevices, input devices, output devices, sensors, etc. In someembodiments, a circuit may take the form of one or more analog circuits,electronic circuits (e.g., integrated circuits (IC), discrete circuits,system on a chip (SOCs) circuits, etc.), telecommunication circuits,hybrid circuits, and any other type of “circuit.” In this regard, the“circuit” may include any type of component for accomplishing orfacilitating achievement of the operations described herein. Forexample, a circuit as described herein may include one or moretransistors, logic gates (e.g., NAND, AND, NOR, OR, XOR, NOT, XNOR,etc.), resistors, multiplexers, registers, capacitors, inductors,diodes, wiring, and so on).

The “circuit” may also include one or more processors communicablycoupled to one or more memory or memory devices. In this regard, the oneor more processors may execute instructions stored in the memory or mayexecute instructions otherwise accessible to the one or more processors.In some embodiments, the one or more processors may be embodied invarious ways. The one or more processors may be constructed in a mannersufficient to perform at least the operations described herein. In someembodiments, the one or more processors may be shared by multiplecircuits (e.g., circuit A and circuit B may comprise or otherwise sharethe same processor which, in some example embodiments, may executeinstructions stored, or otherwise accessed, via different areas ofmemory). Alternatively or additionally, the one or more processors maybe structured to perform or otherwise execute certain operationsindependent of one or more co-processors. In other example embodiments,two or more processors may be coupled via a bus to enable independent,parallel, pipelined, or multi-threaded instruction execution. Eachprocessor may be implemented as one or more general-purpose processors,application specific integrated circuits (ASICs), field programmablegate arrays (FPGAs), digital signal processors (DSPs), or other suitableelectronic data processing components structured to execute instructionsprovided by memory. The one or more processors may take the form of asingle core processor, multi-core processor (e.g., a dual coreprocessor, triple core processor, quad core processor, etc.),microprocessor, etc. In some embodiments, the one or more processors maybe external to the apparatus, for example the one or more processors maybe a remote processor (e.g., a cloud based processor). Alternatively oradditionally, the one or more processors may be internal and/or local tothe apparatus. In this regard, a given circuit or components thereof maybe disposed locally (e.g., as part of a local server, a local computingsystem, etc.) or remotely (e.g., as part of a remote server such as acloud based server). To that end, a “circuit” as described herein mayinclude components that are distributed across one or more locations.

An exemplary system for implementing the overall system or portions ofthe embodiments might include a general purpose computing computers inthe form of computers, including a processing unit, a system memory, anda system bus that couples various system components including the systemmemory to the processing unit. Each memory device may includenon-transient volatile storage media, non-volatile storage media,non-transitory storage media (e.g., one or more volatile and/ornon-volatile memories), etc. In some embodiments, the non-volatile mediamay take the form of ROM, flash memory (e.g., flash memory such as NAND,3D NAND, NOR, 3D NOR, etc.), EEPROM, MRAM, magnetic storage, hard discs,optical discs, etc. In other embodiments, the volatile storage media maytake the form of RAM, TRAM, ZRAM, etc. Combinations of the above arealso included within the scope of machine-readable media. In thisregard, machine-executable instructions comprise, for example,instructions and data which cause a general purpose computer, specialpurpose computer, or special purpose processing machines to perform acertain function or group of functions. Each respective memory devicemay be operable to maintain or otherwise store information relating tothe operations performed by one or more associated circuits, includingprocessor instructions and related data (e.g., database components,object code components, script components, etc.), in accordance with theexample embodiments described herein.

What is claimed is:
 1. An engine assembly comprising: an internalcombustion engine; and a carbon monoxide (CO) sensor unit comprising: aCO sensor controller comprising: a CO sensing circuit configured todetect a level of CO; and a shutdown circuit configured to: receive adetected level of CO; calculate a trailing window average of thedetected level of CO, the trailing window average comprising an averageof the detected level of CO over at least two consecutive samplingloops; determine whether to initiate a shutdown of the internalcombustion engine based on at least the calculated trailing windowaverage and a predetermined trailing window average threshold; andinitiate the shutdown of the internal combustion engine based ondetermining that the trailing window average exceeds the predeterminedtrailing window average threshold.
 2. The engine assembly of claim 1,wherein the shutdown circuit is further configured to: calculate anarray value based on the trailing window average and a currentlydetected level of CO.
 3. The engine assembly of claim 2, wherein thearray value is calculated to be one if the currently detected level ofCO exceeds a threshold above the trailing window average.
 4. The engineassembly of claim 3, wherein the array value is calculated to be zero ifthe currently detected level of CO is less than the threshold above thetrailing window average.
 5. The engine assembly of claim 4, wherein theshutdown circuit is configured to initiate the shutdown of the internalcombustion engine based on determining that the array value exceeds asummed array value and the trailing window average exceeds a lowtrailing window average threshold; wherein the low trailing windowaverage threshold is less than the predetermined trailing window averagethreshold; wherein the summed array value comprises a sum of the arrayvalues within a pre-sized array of array values; wherein the array valueand the summed array value are reset to zero upon detection of thecurrently detected level of CO less than the threshold above thetrailing window average.
 6. The engine assembly of claim 5, wherein theshutdown circuit is configured to initiate the shutdown of the internalcombustion engine only if an internal combustion engine runtime is lessthan an internal combustion engine runtime threshold.
 7. The engineassembly of claim 1, wherein the shutdown circuit monitors the trailingwindow average and the detected level of CO based on at least acontinuous monitoring mode and a start-up monitoring mode; wherein thestart-up monitoring mode is used when an internal combustion engineruntime is less than an internal combustion engine runtime threshold;wherein the continuous monitoring mode is used when the internalcombustion engine runtime is equal to or greater than the internalcombustion engine runtime threshold.
 8. The engine assembly of claim 7,wherein the shutdown circuit switches from monitoring in the start-upmonitoring mode to the continuous monitoring mode upon a trailing windowaverage value drop of more than a threshold drop between a firsttrailing window average value and a subsequent trailing window averagevalue.
 9. The engine assembly of claim 1, wherein the CO sensorcontroller further comprises: an alert circuit configured to: receive anindication from the shutdown circuit to trigger an alert on the internalcombustion engine; and trigger the alert on the internal combustionengine.
 10. The engine assembly of claim 9, further comprising an alertbattery configured to provide power to the alert circuit and the alert.11. The engine assembly of claim 1, wherein the CO sensor unit furthercomprises a sensor power supply configured to receive power from analternator of the engine assembly and provide power to the CO sensorunit.
 12. An engine assembly comprising: an internal combustion engine;and a carbon monoxide (CO) sensor unit comprising: a CO sensorcontroller comprising: a CO sensing circuit configured to detect a levelof CO; and a shutdown circuit configured to: receive a detected level ofCO; receive an indication of internal combustion engine runtime;calculate a trailing window average of the detected level of CO, thetrailing window average comprising an average of the detected level ofCO over at least two consecutive sampling loops; determine whether toinitiate a shutdown of the internal combustion engine based on at least(i) the calculated trailing window average and a predetermined trailingwindow average threshold and (ii) the internal combustion engine runtimeand a predetermined runtime period; initiate the shutdown of theinternal combustion engine based on determining that the trailing windowaverage exceeds the predetermined trailing window average threshold,wherein the predetermined trailing window average threshold is adjustedupon determining that the internal combustion engine runtime exceeds thepredetermined runtime period.
 13. The engine assembly of claim 12,wherein the predetermined trailing window average threshold is adjustedto a higher value upon determining that the internal combustion engineruntime exceeds the predetermined runtime period.
 14. The engineassembly of claim 12, wherein the shutdown circuit is configured toinitiate the shutdown of the internal combustion engine based ondetermining that the trailing window average exceeds the predeterminedtrailing window average threshold over at least five sampling loopswithin a start-up period of the internal combustion engine.
 15. Theengine assembly of claim 12, wherein the shutdown circuit is configuredto initiate the shutdown of the internal combustion engine based ondetermining that the trailing window average exceeds the predeterminedtrailing window average threshold over at least 120 sampling loopswithin a continuous operational period of the internal combustionengine.
 16. A method of controlling an internal combustion engine, themethod comprising: sensing, with a carbon monoxide (CO) sensor, a levelof CO; calculating, with a CO sensor controller in communication withthe CO sensor, a trailing window average of the sensed level of CO overat least two consecutive sampling loops; comparing, with the CO sensorcontroller, the calculated trailing window average of the sensed levelof CO to a predetermined trailing window average threshold; and sending,via the CO sensor controller, a command to terminate operation of theinternal combustion engine from the CO sensor controller to the internalcombustion engine upon determining that the trailing window average ofthe sensed level of CO exceeds the predetermined trailing window averagethreshold.
 17. The method of claim 16, further comprising a step of:receiving, with the CO sensor controller, an indication of currentengine runtime; comparing, with the CO sensor controller, the indicationof current engine runtime against a predetermined runtime period; andadjusting, with the CO sensor controller, the predetermined trailingwindow average threshold based upon the comparison of current engineruntime against the predetermined runtime period.
 18. The method ofclaim 17, wherein the predetermined trailing window average threshold isincreased upon determining that the current engine runtime exceeds thepredetermined runtime period.
 19. The method of claim 18, wherein the COsensor controller sends the command to terminate operation of theinternal combustion engine upon determining that the trailing windowaverage exceeds the predetermined trailing window average over at leastfive sampling loops within a start-up period of the internal combustionengine.
 20. The method of claim 18, wherein the CO sensor controllersends the command to terminate operation of the internal combustionengine upon determining that the trailing window average exceeds thepredetermined trailing window average over at least 120 sampling loopswithin a continuous operational period of the internal combustionengine.